Usually, in a process of manufacturing a group III nitride semiconductor substrate by growing a group III nitride semiconductor layer on a substrate, many dislocations occur in the group III nitride semiconductor layer due to lattice mismatch between a substrate material and a group III nitride semiconductor material. When a GaN film is formed on an Si substrate, the dislocation density on the surface of a GaN layer is 1×109 cm2 to 1×1010 cm2, and even when a sapphire substrate commonly used in recent years is used as a substrate, the dislocation density on the GaN layer surface is about 5×108 cm2. The dislocation may cause a reduction in luminance efficiency when the group III nitride semiconductor substrate is used for an LED and may cause a leak current when used for a power device.
Patent Document 1 describes a manufacturing method for a GaN-based compound semiconductor. The method includes forming a first GaN-based compound semiconductor layer on a substrate, forming discretely an SiN buffer body on the first GaN-based compound semiconductor layer, and forming a second GaN-based compound semiconductor layer on the SiN buffer body. In this technology, it is described that dislocation in the second GaN-based compound semiconductor layer is reduced due to the existence of the SiN buffer body.
Patent Document 2 describes a manufacturing method for a group III nitride semiconductor substrate. The method includes forming an SiO2 layer into a stripe form on an Si substrate and growing a group III nitride semiconductor layer. In this technology, it is described that dislocation is reduced due to lateral growth of the group III nitride semiconductor layer on the SiO2 layer.